The invention relates to the transmission of electrical signals between a stationary portion and a complimentary moving portion of various electromechanical devices. More particularly, the invention relates to an electro-optical non-contacting coupling apparatus for transferring one or more electrical signals between rotating and stationary devices.
Typically, electrical and light signals have been transferred between moving and stationary parts of devices by means of various apparatus which include, for example, slip rings, rotary transformers and/or fiber optic bundles. However, all these coupling apparatus are subject to various undesirable disadvantages, particularly when used in sophisticated, very high speed applications such as, for example, helical scanner systems in video tape recorders.
To illustrate, slip rings are subject to wear, particularly in very high speed rotary devices. Slip rings further are prone to the generation of electrical noises and have cooling problems.
Rotary transformers are non-linear, have no response to a DC component, and are complex and expensive devices which are difficult to package and fabricate, particularly in a rotating head configuration such as used, for example, in the video tape recorders of previous mention. That is, while rotary transformers solve some of the problems of slip ring devices, they require considerable electrical power to function properly, and are subject to signal attenuation. For example, they can induce signal distortions since they rely upon the transmission of electromagnetic energy across an air gap between their rotating and stationary parts, wherein the air gap and thus the transmission can be influenced by adjacent magnetic materials. Signal attenuation also is caused by the mediocre bandwidth characteristics of the rotary transformer, whose response starts to roll-off prematurely to signal roll-off. In addition, in an application having many data channels, the complexity and bulkiness of rotary transformers would prohibit their use.
Typical fiber optic bundle electro-optical devices also are difficult to package and fabricate and have not successfully been used to date in precision, high speed environments such as tape recorder rotating head apparatus.